Exhaust-Cleaning Device For Internal Combustion Engines Besides a Vehicle Comprising Such an Exhaust-Cleaning Device and an Extension for Exhaust-Cleaning Devices

ABSTRACT

An exhaust-cleaning device for internal combustion engines having varying exhaust amount, which is intended to constitute a part of an exhaust system co-operating with an engine includes a main converter and a pre-converter located upstream the main converter, seen in the direction that exhaust fumes are intended to pass the exhaust-cleaning device. The exhaust-cleaning device is distinguished by a bypass arranged in the area of the pre-converter. The bypass includes a first opening upstream the pre-converter, and a second opening downstream the pre-converter and upstream the main converter, so that at least a part of the exhaust fumes passes past the pre-converter without passing therethrough. An extension for an exhaust-cleaning device and a vehicle including such an exhaust-cleaning device are disclosed.

TECHNICAL FIELD OF THE INVENTION

This invention relates to an exhaust-cleaning device for internal combustion engines having varying exhaust amount, which is intended to constitute a part of an exhaust system co-operating with an engine and which comprises a main converter and a pre-converter, which is located upstream the main converter, seen in the direction that the exhaust fumes are intended to pass the exhaust-cleaning device, in the area of the pre-converter a bypass being arranged, which includes a first opening, which mouths upstream the pre-converter, and a second opening, which mouths downstream the pre-converter and upstream the main converter, so that at least a part of the exhaust fumes should be able to pass past the pre-converter without passing through the same.

Exhaust-cleaning devices of the kind in question have the purpose of decreasing the amount of harmful substances, for instance carbon monoxide, hydrocarbons, nitric oxides, etc., that exit an internal combustion engine during operation.

BACKGROUND OF THE INVENTION AND PRIOR ART

The present invention has the background thereof in the need for obtaining a requisite cleaning of the exhaust fumes that exit an engine during operation. A recognized way of providing the exhaust cleaning is to use an exhaust-cleaning device that includes a catalyst, which accelerates the chemical reactions taking place upon combustion. A conventional catalyst attains a good working effect when the same has a temperature of about 300° C. Thus, problems arise upon, for instance, cold starting if only one catalyst is used, since a great quantity of harmful components have the time to pass the same before a sufficiently high temperature has been attained.

In order to obtain a good cleaning function from start, an exhaust-cleaning device comprising a main converter as well as a pre-converter is therefore used. The pre-converter is located between the engine and the main converter and is generally relatively small and tight, in comparison with the main converter, for a quick heating of the same should be effected. Thus, a pre-converter provides a good exhaust cleaning already a short time after a cold starting of an engine. However, a disadvantage is that the pre-converter should be located as near the engine as possible, in order to guarantee good cleaning, which may give unnecessary construction restrictions as regards engine compartment, etc.

An annoying disadvantage, which also is a consequence of the introduction of a small, tight pre-converter in the exhaust system, is that the same builds up a large back-pressure upstream the same, more precisely as a consequence of the engine forming large amounts of exhaust fumes having high flow velocity upon high power output of the same. The main converter is dimensioned to clean the exhaust fumes during such conditions, but because of the nature and location of the pre-converter, the exhaust fumes are slowed down and the pressure upstream the pre-converter accordingly increases. Upon sustained high power output, the risk of the pre-converter being damaged is imminent, i.e., that the pre-converter is supercharged and “stressed”, with the result that the same is consumed prematurely and/or melts. It is also a disadvantage that the pre-converter and the main converter, as a consequence of the constructions thereof, usually are placed relatively far from each other along the exhaust system. The exhaust fumes are cooled down upon the contact with the exhaust pipe between the converters, the main converter running the risk of not attaining a requisite temperature sufficiently fast. Frequently, the exhaust pipe between the converters has a considerably smaller cross section area than the converters, which affects the flow and creates additional back-pressure in the exhaust system.

OBJECTS AND FEATURES OF THE INVENTION

The present invention aims at obviating the above-mentioned disadvantages of previously known exhaust-cleaning devices, and providing an improved exhaust-cleaning device. Therefore, a primary object of the invention is to provide an exhaust-cleaning device that makes it possible to clean the exhaust fumes by means of, on one hand, a pre-converter upon cold startings and small exhaust flows, and on the other hand a main converter upon large exhaust flows. A second object of the invention is to provide an exhaust-cleaning device, the pre-converter of which is not super-charged at large exhaust flows. It is also an object of the invention to provide an exhaust-cleaning device that allows quick heating of the main converter. Furthermore, it is an object of the invention to provide an exhaust-cleaning device, the pre-converter of which is heated quickly upon start, and is cooled down during operation in order to counteract overheating of the same. An additional object of the invention is to provide an exhaust-cleaning device that also presents a sound-absorbing effect.

According to the invention, at least the primary object is attained by means of the exhaust-cleaning device defined by way of introduction, which is characterized in that in the area of the pre-converter a bypass is arranged, which includes a first opening, which mouths upstream the pre-converter, and a second opening, which mouths downstream the pre-converter and upstream the main converter, so that at least a part of the exhaust fumes should be able to pass past the pre-converter without passing through the same. The exhaust-cleaning device is principally arranged in this way, for allowing the exhaust fumes upon large exhaust flows to pass through the main converter without first having passed through the pre-converter. Preferably, the exhaust-cleaning device is arranged in such a way that the pre-converter is accommodated in a housing, which has a larger cross section area than the pre-converter, the bypass consisting of the preferably ring-shaped space that is formed between the inside of the housing and the outside of the pre-converter.

Preferably, said housing has an inlet sleeve, which tapers in the direction downstream, seen in the direction of flow of the exhaust fumes, at the same time as the pre-converter has a collar, which projects in the direction toward the inlet sleeve and which tapers in the direction upstream. The advantage of this construction is that the exhaust fumes at small flows, for instance upon start, are concentrated by the inlet sleeve and captured by the collar, which entails that only at large flows the exhaust fumes are forced to pass through the bypass in larger amounts. Thanks to the bypass, the stress on the pre-converter decreases at large exhaust flows, which increases the service life of the same.

Preferred embodiments of the exhaust-cleaning device according to the invention are further seen in the dependent claims 2-8, and in the subsequent, detailed description of preferred embodiments.

In a second aspect, the invention also relates to an extension for an exhaust-cleaning device. The features of this extension are defined in the independent claim 9.

In a third aspect, the invention also relates to a vehicle. The features of this vehicle are seen in the independent claim 10.

BRIEF DESCRIPTION OF THE APPENDED DRAWINGS

In the drawings:

FIG. 1 is a schematic longitudinal section of an exhaust-cleaning device according to the invention,

FIG. 2 is a schematic cross section A-A in FIG. 1,

FIG. 3 is a schematic longitudinal section of an exhaust-cleaning device according to an alternative embodiment, and

FIG. 4 is a schematic longitudinal section of an exhaust-cleaning device according to prior art.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

In FIG. 1, an exhaust-cleaning device, generally designated 1, is shown, which comprises a main converter 2 and a pre-converter 3, which is retreated from said main converter 2 in the direction upstream, seen in the direction of flow of the exhaust fumes. According to a preferred embodiment, the exhaust-cleaning device 1 includes a housing 4, which accommodates said pre-converter 3 and main converter 2, and with which an inlet sleeve 5 and an outlet sleeve 6 are connected. The inlet sleeve 5 and the outlet sleeve 6 are arranged to be connected to two exhaust pipes 7 included in an exhaust system. In other words, the exhaust-cleaning device 1 should be regarded as constituting a part of a larger exhaust system. The exhaust system is preferably arranged on a vehicle, for instance an automobile, lorry, motor cycle, etc., and extends from an internal combustion engine (not shown) to a free terminating end (not shown), through which the cleaned exhaust fumes may be let out. It should also be pointed out that the exhaust pipes 7 may be connected to, for instance, one or more silencers and/or other components (not shown).

In the embodiment shown in the drawings, each catalyst 2, 3 has a cylindrical basic shape, with the pre-converter 3 having a-diameter of about 100 mm and a length of about 100 mm. The size of the pre-converter 3 may, however, vary much depending on the size of the engine and remaining parts of the exhaust system. It should be mentioned that the length as well as the diameter of a pre-converter 3 preferably should be within the interval of 30-200 mm. The active substance of the converters 2, 3 consists of a substrate, having a catalytic capacity, which is accommodated in a tubular casing.

Now reference is made also to FIG. 2. The pre-converter 3 has a smaller cross section area than the housing 4, a ring-shaped bypass 8 being formed between the outside of the pre-converter 3 and the inside of the housing 4. Furthermore, in a preferred embodiment the pre-converter 3 is radially retreated from the housing 4 via a number of stays 9, preferably in such a way that the same is concentrically arranged with said housing 4. The bypass 8 includes a first opening 10, which mouths upstream the pre-converter 3, seen in the direction of flow of the exhaust fumes. Furthermore, the bypass 8 also includes a second opening 11, which mouths downstream the pre-converter 3 and upstream the main converter 2. The main converter 2, in contrast to the pre-converter 3, occupies the entire cross section area of the housing 4, in such a way that the exhaust fumes are forced to pass through the main converter 2. This entails that the exhaust fumes always will pass through the exhaust-cleaning device 1 and be cleaned, at least partially, even if the pre-converter 3 would be clogged or in another way become unusable.

Furthermore, the inlet sleeve 5 preferably extends about 30 mm into the housing 4, primarily in order to direct the exhaust flow toward the pre-converter 3. In an additional preferred embodiment, the cross section area of the inlet sleeve 5 decreases in the direction downstream, in order to reinforce the centering effect. In addition, the pre-converter 3 may be provided with a collar 12, which extends in the direction upstream toward the inlet sleeve, and the cross section area of which decreases in the direction upstream, in order to, at small amounts of flow get a converging effect and at large amounts of flow get a diverging effect. The smallest diameter of the inlet sleeve 5 should exceed 15 mm and the smallest diameter of the collar 12 should exceed 30 mm. The smallest diameter of the inlet sleeve 5 should at least be smaller than the smallest diameter of the collar 12, in other words the free, rear end of the inlet sleeve 5 preferably ends radially inside said collar 12, in order to get maximum converging effect at small amounts of flow. The axial distance between the inlet sleeve 5 and the collar 12 should preferably be smaller than 90 mm and greater than 0 mm.

The fact that the pre-converter 3 and the main converter 2 are accommodated in the same housing 4, entails that the axial distance between them may be decreased, from previously conventional distances of about 100-200 mm to about 10-20 mm. An extreme is that the pre-converter 3 and the main converter 2 abut against each other. The decreased distance entails that the exhaust-cleaning device 1 according to the invention will be able to be constructed so that the same occupies less space than exhaust-cleaning devices according to prior art.

Now reference is made to FIG. 3, which shows an alternative embodiment of the exhaust-cleaning device 1 according to the invention. In contrast to the embodiment according to FIG. 1, the pre-converter 3 and the main converter 2 are axially spaced-apart in the same way as exhaust-cleaning devices 1 according to prior art (see FIG. 4). In other respects, the pre-converter 3 is accommodated in the housing 4 and radially retreated from the same by means of a number of stays 9. The embodiment shown in FIG. 3 is suitable in the case when the design of a vehicle (not shown) in other respects does not allow that the general construction of the exhaust-cleaning device 1 is changed, but the pre-converter 3 and the main converter 2 have to be spaced-apart in order to be able to be accommodated in, for instance, an engine compartment (not shown).

Now reference is made again to FIGS. 1 and 2. In the schematic illustration of the preferred embodiment, the cross section areas of the bypass 8 and the pre-converter 3 are approximately equally large. However, it should be pointed out that their mutual proportions may vary considerably, depending on which flow ratio that is desired to be attained through the pre-converter 3 and the bypass 8, respectively.

THE FUNCTION AND ADVANTAGES OF THE INVENTION

Suppose that the starting point is that a vehicle, the engine of which has not been used for a significant period of time, i.e., that the engine and remaining parts of the exhaust system and engine compartment are cold. Suppose further that the engine is started in a conventional way. Immediately after start, a small quantity of hot exhaust fumes flow from the engine through the exhaust pipe 7 and into the exhaust-cleaning device 1 through the inlet sleeve 5, which directs the exhaust flow toward a central point on the pre-converter 3. The collar 12 on the pre-converter helps to collect the exhaust fumes, and counteracts that the exhaust fumes flow out into the bypass 8. In this way, a quick heating of the pre-converter 3 is obtained. An advantage of the inlet sleeve 5 tapering in the direction downstream is that the hot exhaust fumes are concentrated, which entails that the central part of the pre-converter 3 is heated quickly.

The bypass 8 is also an advantage in an initial stage, in spite of the same in this position not being used for exhaust passage, since the space between the pre-converter 3 and the housing 4 insulates the pre-converter 3 from being cooled down by the surrounding air outside the housing 4. As a consequence of the pre-converter 3 being heated faster than traditional pre-converters, the same may be placed at a distance from the engine that is greater than conventional distances between an engine and a pre-converter. Consequently, this gives greater flexibility as regards the location of the exhaust-cleaning device 1. When the exhaust fumes have passed through and been cleaned by the pre-converter 3, they flow on toward the main converter 2 for additional cleaning. According to the preferred embodiment, which is shown in FIG. 1, the short distance between the pre-converter 3 and the main converter 2 entails that the hot exhaust fumes having passed through the pre-converter 3 still are gathered and centred, which also gives a quick heating of the main converter 2.

Suppose now that higher power is extracted from the engine, which result in larger exhaust amounts flowing from the same and toward the exhaust-cleaning device 1. When the pre-converter 3 is relatively tight and small, a back-pressure will arise upstream the same, but thanks to the bypass 8, the exhaust fumes will now follow “the line of least resistance” and “choose” to pass through the bypass 8 and further toward the main converter 2, which in contrast to the pre-converter 3 is dimensioned to cope with large amounts of flow. When a back-pressure has been built up inside the collar 12, the conical shape thereof, as is shown in FIGS. 1 and 3, helps to facilitate for the exhaust fumes to flow into the bypass 8.

Previously, the pre-converter 3 has been a bottleneck in exhaust systems upon great power output and the entire exhaust flow has been forced through the same. This has resulted in the pre-converter 3 having been made larger than what has been required in order to clean the exhaust fumes upon cold starting and at small flows. Hence, the bypass 8 entails that the pre-converter 3 can be made smaller and tighter than what has been possible previously, which involves that the same will attain sufficiently high working temperature faster than previously.

When the exhaust fumes pass through the bypass 8, a cooling effect arises on the pre-converter 3, as a consequence of the exhaust fumes in the bypass 8 having a lower temperature than the pre-converter 3. Thanks to this cooling, the service life of the pre-converter 3 is considerably extended in spite of high power outputs from the engine. The bypass 8 and the housing 4 also work as a heat shield between the pre-converter 3 and surrounding equipment in the engine compartment, which entails that the exhaust-cleaning device 1 requires a smaller amount of conventional heat insulation in order not to damage the surrounding equipment.

It has also has been shown that the exhaust-cleaning device 1 according to the invention has a sound-absorbing effect, among other things as a consequence of miscellaneous area alterations and windings in the exhaust-cleaning device 1. As a consequence of this, the size of a possibly occurring silencer can be decreased, which entails that the total back-pressure in the exhaust system is additionally decreased.

FEASIBLE MODIFICATIONS OF THE INVENTION

The invention is not only limited to the embodiments described above and shown in the drawings. Thus, the exhaust-cleaning device as well as the extension may be modified in miscellaneous ways within the scope of the subsequent claims.

Particularly, it should be mentioned that the different converter elements do not necessarily have to be cylindrical as is shown in the drawings, but the same may have any other suitable shape that can fulfil the function of cleaning the exhaust fumes from harmful substances. It should be pointed out that the concept “bypass” should be interpreted in the widest sense thereof, and accordingly be regarded to include each form of component that can fulfil the function of leading the exhaust fumes past the pre-converter.

It should also be pointed out that the bypass according to the invention not only should be associated with catalysts of some specific type, but it should be realized that the bypass works together with all feasible catalysts. That is, not only catalysts that are mounted on a movable vehicle, but also catalysts that are connected to stationary engines, should be regarded to be included in the invention. It should be mentioned that the flow ratio between the pre-converter and the bypass, in addition to as a result of altered geometry parameters, also may be adjusted by some movable element, such as a spring-loaded flap that is opened when the back-pressure exceeds a certain limit value, or an actuatable valve, suitably placed at the front opening of the bypass.

The pre-converter and the main converter do not have to be mounted in the same housing, as is shown in the figures, but they may constitute individual components, each one of which constitutes a part of an exhaust system and between which there is an exhaust pipe.

A bypass for a conventional exhaust-cleaning device according to prior art may be realized by means of an extension. Such an extension should comprise a first opening, which should be arranged to co-operate with a hole, which are arranged upstream the pre-converter. In addition, the extension should comprise a second opening, which should be arranged to co-operate with a hole, which are arranged downstream the pre-converter and upstream the main converter. The extension may consist of a genuine bypass, in the form of, for instance, a narrow pipe, having openings in opposite ends, or of a tube that has a diameter being larger than the diameter of the pre-converter and that in co-operation with said pre-converter forms the bypass. Imperative for the extension is that a bypass is formed, through which the exhaust fumes can pass without needing to pass through the pre-converter. 

1. Exhaust-cleaning device for internal combustion engines having varying exhaust amount, which is intended to constitute a part of an exhaust system cooperating with an engine and which comprises a main converter (2) and a pre-converter (3), which is located upstream the main converter (2), seen in the direction that the exhaust fumes are intended to pass the exhaust-cleaning device, in the area of the pre-converter (3) a bypass (8) being arranged, which includes a first opening (10), which mouths upstream the pre-converter (3), and a second opening (11), which mouths downstream the pre-converter (3) and upstream the main converter (2), so that at least a part of the exhaust fumes should be able to pass past the pre-converter (3) without passing through the same, characterized in that, in the direction upstream from the pre-converter (3), a collar (12) projects, which tapers in the direction upstream.
 2. Exhaust-cleaning device according to claim 1, characterized in that the pre-converter (3) is accommodated in a housing (4), the cross section area of which is larger than the cross section area of said pre-converter (3), a space formed between the pre-converter (3) and the housing (4) constituting said bypass (8).
 3. Exhaust-cleaning device according to claim 2, characterized in that the pre-converter (3) is radially retreated from said housing (4) by means of a number of stays (9).
 4. Exhaust-cleaning device according to claim 2, characterized in that the pre-converter (3) is concentrically arranged in relation to the housing (4).
 5. Exhaust-cleaning device according to claim 1, characterized in that the same includes an inlet sleeve (5), which tapers in the direction downstream.
 6. Exhaust-cleaning device according to claim 5, characterized in that said inlet sleeve (5), in the direction downstream, ends radially inside said collar (12).
 7. Exhaust-cleaning device according to claim 2, characterized in that the pre-converter (3) and the main converter (2) are accommodated in said housing (4).
 8. Exhaust-cleaning device according to claim 1, characterized in that the axial distance between the pre-converter (3) and the main converter (2) is smaller than 20 mm.
 9. Extension for an exhaust-cleaning device (1), which comprises a main converter (2) and a pre-converter (3), which is located upstream the main converter (2), seen in the direction that the exhaust fumes are intended to flow, characterized in that the same includes a first opening (10), which is connectable upstream the pre-converter (3), and a second opening (11), which is connectable downstream the pre-converter (3) and upstream the main converter (2), the extension forming a bypass (8), and in the direction upstream from the pre-converter (3), a collar (12) projecting, which tapers in the direction upstream.
 10. Vehicle comprising an engine and an exhaust system extending from the same, which exhaust system comprises an exhaust-cleaning device (1), which includes a main converter (2) and a pre-converter (3), which is located upstream the main converter (2), seen in the direction of flow of the exhaust fumes, the exhaust-cleaning device (1) comprising a bypass (8), which includes a first opening (10), which mouths upstream the pre-converter (3), and a second opening (11), which mouths downstream the pre-converter (3) and upstream the main converter (2), so that the exhaust fumes should be able to pass past the pre-converter (3) without passing through the same, characterized in that, in the direction upstream from the pre-converter (3), a collar (12) projects, which tapers in the direction upstream.
 11. Exhaust-cleaning device according to claim 3, characterized in that the pre-converter (3) is concentrically arranged in relation to the housing (4).
 12. Exhaust-cleaning device according to claim 2, characterized in that the same includes an inlet sleeve (5), which tapers in the direction downstream.
 13. Exhaust-cleaning device according to claim 3, characterized in that the same includes an inlet sleeve (5), which tapers in the direction downstream.
 14. Exhaust-cleaning device according to claim 4, characterized in that the same includes an inlet sleeve (5), which tapers in the direction downstream.
 15. Exhaust-cleaning device according to claim 3, characterized in that the pre-converter (3) and the main converter (2) are accommodated in said housing (4).
 16. Exhaust-cleaning device according to claim 4, characterized in that the pre-converter (3) and the main converter (2) are accommodated in said housing (4).
 17. Exhaust-cleaning device according to claim 5, characterized in that the pre-converter (3) and the main converter (2) are accommodated in said housing (4).
 18. Exhaust-cleaning device according to claim 6, characterized in that the pre-converter (3) and the main converter (2) are accommodated in said housing (4). 